Battery separator element containing efficiency improving additives

ABSTRACT

A recombinant battery element of a lead acid battery including a negative plate, a positive plate and a separator having an additive associated with the separator that improves the overall efficiency of the lead acid battery.

RELATED APPLICATIONS

[0001] This application is a division application of application Ser.No. 09/045,725, filed Mar. 20, 1998. This earlier filed application isincorporated in its entirety herein by reference.

BACKGROUND OF THE INVENTION

[0002] The present invention relates to an improved lead acid batteryelement containing metal impurity inhibiting polymeric additives, whichare added to the positive active material, negative active materialand/or battery separator to inhibit the detrimental effects of certainmetals on the efficiency of a lead acid battery, particularly thenegative plate battery element and to macroporous additives that enhanceactive material utilization efficiency and improvement in theutilization of sulfuric acid electrolyte necessary for the dischargereaction of a lead acid battery.

[0003] Further the present invention relates to a recombinant batteryseparator element, which improves utilization efficiency of the sulfuricacid electrolyte in a valve regulated recombinant lead acid battery. Inbrief the separator battery elements include the addition of porouscontaining particle additives to the separator of a valve regulatedrecombinant lead acid battery to improve the overall utilizationefficiency and the utilization of sulfuric acid electrolyte duringcharge/discharge of the battery.

[0004] Separators used for valve regulated or as also referred to sealedlead-acid batteries operating on the oxygen recombination principle,i.e. oxygen recombinant batteries, typically operate with a limitedamount of sulfuric acid electrolyte, i.e. only having electrolyte withinthe separator and the pores of the negative and positive activematerial. Unlike flooded batteries which have excess electrolyte andgenerally means for water addition, the design of valve regulatedrecombinant batteries do not have provisions for the addition of waterduring the life of the battery. Further, the battery is designed so thatthe oxygen generated at the positive electrode during charging isrecombined to form water at the negative electrode. Separators used forvalve regulated lead acid batteries typically include one or more layersof highly absorptive porous mats typically having a mix of fibers. Theporosity of the separator is designed such to allow oxygen to transportdirectly through the separator for reaction at the negative electrode.The design requirements of limited sulfuric acid electrolyte and oxygenrecombination at the negative electrode gives rise to a number ofserious problems affecting valve regulated lead acid batteries includingelectrolyte stratification in the separator particularly in the verticaldirection and excessive transport of oxygen to the negative plate beforethe negative plate can be fully recharged. Thus, published studies haveshown that the stratification of the electrolyte brings about adifference in the electrolyte concentration between the upper and lowerportions of the separator thereby reducing the amount of sulfate ionrequired for the electrochemical reactions during discharge of thebattery, i.e. both positive and negative plate active material areconverted to lead sulfate. Further, the properties of the separator canaffect the height at which the electrolyte rises and the speed or rateof electrolyte absorption and diffusion both upward and downwardparticularly during electrolyte initial fill of the battery and sulfatereaction during discharge particularly high rate discharges. Thus, theseparator for valve regulated batteries should minimize stratificationeffects particularly during repeated charge/discharge cycles and providefor rapid wicking of the electrolyte during fill of the battery.Further, the separator should allow control of the oxygen from thepositive electrode to the negative electrode in order to improve thecharging efficiency of the negative plate as it approaches full charge.In addition the separator must provide for controlled wetability inorder to minimize stratification, provide for ease of electrolytefilling and to control oxygen recombination transport for improvednegative plate charging.

[0005] Metal impurities can be introduced into a lead acid batterythrough the use of any of the materials used in the manufacture of thebattery. For example, metal impurities can be introduced in the lead andleady oxides used in the manufacture of the active material, thematerials of construction including the lead grids, alloying agents,electrolyte and water. Nearly all metallic impurities, if they arenobler than lead, have a smaller hydrogen overvoltage than pure lead.Therefore, they increase hydrogen evolution even if they are depositedin minute concentrations on the surface of the negative plates. Thesemetals cause a continued gas evolution even after charging is completed.Hydrogen is evolved on the deposited metal with low hydrogenovervoltage, which can be short-circuited with lead. The effect of metalon the gassing particularly postcharge gassing decreases in thefollowing sequence: Pt, Au, Te, Ni, Co, Fe, Cu, Sb, Ag, Bi and Sn. Thepresence of 0.3 ppm of platinum in the acid can cause a doubling of theself-discharge rate. Tin can produce this effect at 0.1%. Freshlydeposited antimony is especially active. Besides the discharge of thenegative plates with concomitant hydrogen evolution, these materialsalso move the end of charge voltage of the negative plates toward morepositive values. The hydrogen evolution increases with rising aciddensity. Because the hydrogen overvoltage decreases with temperature,the self-discharge increases.

SUMMARY OF THE INVENTION

[0006] A new battery element which inhibits the detrimental effect ofsoluble metal impurity on the negative plate has been discovered. Inbrief, the battery elements include the addition of an organic polymerhaving functional groups with a preferential affinity for the metalimpurity in the cation or anion state, to the positive active material,the negative active material or the separator which separates thepositive and negative plates within a lead acid battery and whichtypically is a reservoir for sulfuric acid electrolyte.

[0007] A new recombinant battery separator element, which improvesutilization efficiency of the sulfuric acid electrolyte in a lead acidbattery, has been discovered. In brief the separator battery elementincludes the addition of porous organic particle additives havingfunctional groups, which associate with the sulfuric acid electrolyte tocontrol oxygen diffusion through the separator, improve electrolytedistribution in the separator and improve overall battery utilizationefficiency, particularly the utilization of sulfuric acid electrolyteduring repeated charge/discharge cycles of the battery.

[0008] A new battery element, which improves utilization efficiency ofthe active material in a lead acid battery has been discovered. Inbrief, the battery elements include the addition of macroporouscontaining particle additives to the active material in the positive ornegative plates of a lead acid battery to improve overall utilizationefficiency and the utilization of sulfuric acid electrolyte duringdischarge of the battery.

[0009] A new recombinant battery separator element, which improvesutilization efficiency of the battery, particularly the utilization ofthe sulfuric acid electrolyte in a lead acid battery, has beendiscovered. In brief the separator element includes the addition ofmacroporous containing particle additives to the separator of a leadacid battery to improve overall battery utilization efficiency,particularly the utilization of sulfuric acid electrolyte duringrepeated charge/discharge cycles of the battery.

DETAILED DESCRIPTION OF THE INVENTION

[0010] In one broad aspect, the present battery elements comprise theaddition of an organic polymer containing functional groups with apreferential affinity for metal impurity in the cation or anion state tothe positive active material, the negative active material and/or theseparator which separates the positive plates from the negative platesin a lead acid battery. In a preferred embodiment, the organic polymersare porous, i.e. the porosity of the polymer allows the soluble metalimpurity in the electrolyte to contact both the outer surface of thepolymers and the internal surfaces created by the porosity of theorganic polymers. The functional groups having a preferential affinityfor metal impurity include both functional groups on the outer surfaceand internal surfaces in contact with soluble metal impurity in theelectrolyte. The metal impurity inhibiting additives are typicallyincorporated into the negative active material, the positive activematerial and/or the separator in an amount sufficient to inhibit thedetrimental effects of metal impurity on the negative plate.

[0011] In another broad aspect, the present separator battery elementscomprise the addition of porous organic polymer particles containingfunctional groups, which associate with the sulfuric acid electrolyte tocontrol oxygen transport from the positive to the negative plate duringcharging and provide for improvement in electrolyte distribution in theseparator. In a preferred embodiment the particles have larger diametersand larger pores at the acid molarity concentrations of discharge whencompared to the size of the particles at the acid molarity at fullcharge. In a further preferred embodiment the electrolyte contacts boththe outer surfaces of the polymers and the internal surfaces created bythe porosity of the organic polymers. The functional groups having apreferential affinity for sulfuric acid electrolyte include bothfunctional groups on the outer surface and internal surfaces in contactwith the electrolyte. The particles are incorporated in the separator inan amount sufficient to control the oxygen transport through theseparator and improve overall electrolyte utilization efficiency in thebattery.

[0012] In another broad aspect, the present battery elements comprisethe addition of macroporous additives to the active material present inthe positive and/or negative plates in a lead acid battery. In a furtherpreferred embodiment, the macroporous particles have a reduced affinityfor bonding with the active material in the positive and negativeplates, i.e. a substantially reduced bonding of lead ion with thepolymeric functional groups.

[0013] In another broad aspect, the present recombinant separatorelements comprise the addition of elongated macroporous additiveparticles to the separator to improve overall electrolyte distributionin the separator and improve overall utilization of sulfuric acidelectrolyte in the battery. In brief, the separator elements include theaddition of macroporous containing particles to reduce electrolytestratification in the separator and improve overall distribution andrate of distribution of the electrolyte in the separator. In a furtherpreferred embodiment, the macroporous particles have controlled surfacewetability, preferably a combination of hydrophilic and hydrophobicsurface properties to improve overall distribution and rate ofdistribution of the electrolyte in the separator.

[0014] As set forth above, metal impurities can be introduced into thebattery during the battery manufacturing process, particularly in thestarting materials used for battery manufacture. Many of the metalimpurities can exist in the anion or cation form i.e. a negative orpositive charge respectively in sulfate solutions such as thatrepresented by sulfuric acid electrolyte. Depending on the molarity ofthe sulfuric acid electrolyte and the metal impurity, such cation/anionforms can change as the molarity changes. Depending on such sulfuricacid molarity, it is believed that platinum, gold, thallium, nickel,cobalt, iron, copper, antimony, silver, bismuth and tin can exist asanions even though such existence as anions may be weak or unstable.Further, such anion forms may predominant at the sulfuric acidelectrolyte concentrations, which exist after battery charging. One ofthe particularly detrimental metal impurities is platinum.

[0015] As set forth above, such metal impurities can be introduced intothe lead acid battery during manufacturing. In a number of batterydesigns, grid materials not having antimony as an alloying agent areused for battery manufacture. However, even in these types of batteriesusing nonantimony containing grids, antimony can be introduced as animpurity in the starting materials for battery manufacture including thestarting lead and leady oxide type materials.

[0016] As set forth above, antimony, which is present in the positivegrid as an alloying agent, can be oxidized and/or corroded to form asoluble antimony ion, which diffuses and/or migrates to the negativeplate. Antimony at the negative plate can produce a number ofdetrimental problems such as self discharge and gassing particularlyhydrogen formation. Antimony ion from the positive grid can exist inboth the anion and cation form, i.e. a negative or positive chargerespectively. It is believed that the form of the anion or cation isdependent on the oxidation state of the antimony, i.e. +3 or +5, themolarity of the sulfuric acid and the battery voltage. For example, itis believed that antimony can exist as SbO2+ cation and SbO3− anion inthe antimony +5 state and as SbOSO4−, Sb(SO4)²⁻ SbO2 in the antimony +3state. These +3 anion forms are believed to exist when the molarity ofthe sulfuric acid is greater than one but may not exist at the fullyrecharged battery voltage. In addition, it is believed that antimony mayexist as Sb+3 or SbO+ in the antimony +3 state again depending onmolarity and battery voltage. As set forth above, the sulfuric acidelectrolyte participates in the discharge reactions taking place in thelead acid battery. Thus, the wt % sulfuric acid can decrease from 30-40wt % sulfuric acid to from 10-14 wt % sulfuric acid depending on thetype of battery design and the initial sulfuric acid concentration inthe electrolyte. The amount of sulfuric acid remaining will be dependenton the percent of discharge of the battery with less sulfuric acidremaining when batteries are discharged to 80% or more.

[0017] The organic polymers having functional groups with a preferentialaffinity for metal impurities in the anion or cation state inhibit thedetrimental effects of soluble metal impurity on the negative plate.While the exact mechanism of inhibition is not known, it is believedthat the metal impurity anion or cation is bound by the functional groupsuch as by the anion replacing the anion present on the functional groupin an anionic polymer or by a cation replacing the cation when theorganic polymer contains cation functional groups. Although anion and/orcation replacement is believed to be one mechanism for inhibiting theadverse effects of metal impurity ions, metal impurities can also formcomplexes and/or be solvated to inhibit the detrimental effect of metalimpurities on the negative plate and such mechanisms are included inthen the term inhibiting. One of the major discoveries of the batteryelements of this invention is the inhibition of metal impurities overthe varying sulfuric acid molarities and battery potentials (voltages)that occur during the charge discharge reactions in a lead acid battery.Further it has been discovered that the metal impurity which has beeninhibited by the organic polymer additive is not substantially anddetrimentally desorbed and/or released from the polymer under thesulfuric acid molarity and battery voltage conditions and changes in alead acid battery, that is the metal impurity inhibition continuesduring a plurality of charge/discharge reactions within the battery.

[0018] As set forth above, the organic polymers containing functionalgroups can introduce cations and/or anions into the battery elementwhich cations or anions can be displaced by the metal impurity anionand/or cation. Further, the affinity of the organic polymer having suchmetal impurity inhibiting functional groups have a stronger bindingand/or complex formation and/or salvation of metal impurity ions whencompared to any intermediate soluble lead ions such as lead +2 which maybe formed during the conversion of solid lead, solid lead peroxide toinsoluble lead sulfate. As is known by those having skill within thelead acid battery art, cations and/or anions which are displaced bymetal impurity cations or anions should not introduce any substantialdetrimental effects on battery performance.

[0019] As set forth above, one of the classes of organic polymers hasfunctionality, which have affinity for metal impurity in the cationform. The metal impurity cation displaces the cation associated with thefunctional group. Typically, the cation displaced can be hydrogen ionor, for example, sodium ion. The organic polymers having such cationfunctionality can be further classified as strongly acidic cationpolymers or weakly acidic cation polymers. Particularly preferredstrongly acidic cation polymers are those containing sulfonic acidgroups or their sodium salt i.e. sulfonic groups preferably in thehydrogen form. Typical examples of polymers containing the sulfonic acidand/or sulfonate functionality are those derived from polystyrenecrosslinked divinylbenzene, phenol-formaldehyde polymers and other likearomatic containing polymers. As set forth above the organic polymer canhave different functional groups such as functional groups containingstrongly acidic functionality such as sulphonic and phosphonicfunctionality on the same organic polymer.

[0020] As set forth above, strongly acidic cation polymers are preferredfor inhibiting the effects of metal impurities. A particularly preferredfunctionality on the polymer is phosphonic acid and/or phosphonate herein after referred to as phosphonic functionality. Typical examples ofsuch functionality are:

[0021] where R is typically hydrogen or sodium ion, preferably hydrogen.

[0022] In general the phosphonic functionality can be incorporated intothe polymer matrix by chemical reaction including grafting of suchfunctionality, on for example the aromatic portion of polystyrene and/orphenol-formaldehyde polymers. In addition, the functionality can beincorporated by the copolymerization unsaturated vinylmono or gem ofphosphonic acid or ester monomers with other monomers patricularlystyrene, with still other monomers such as acrylate or acrylovitriletogether with a cross-linking agent such as divinylbenzene. A typicalmonomer used for such copolymerization is vinylidene diphosphonic acidor the ester thereof to produce gem phosphonic functionality. Furtherexamples of such polymers are polymers having a plurality of aminoalkylene, phosphonic acid or phosphonate associated with the organicpolymer.

[0023] As set forth above bis-derivatives are also useful includingimino-bis(methylenephosphonic acid). The particularly preferredfunctionality is amino methylelephosphonic acid groups on polystyrenecross-linked with divinylbenzene.

[0024] As set forth above, phosphonic functionality can be incorporatedinto the polymer by reaction with an existing polymermatrix or bycopolymerization of for example a vinyl phosphonic monomer. A preferedpolymer is one containing polymerized styrene monomer either as a homepolymer or an inter polymer with other polymerized monomeric units. Suchpolymers containg polymerized styrene are generally referred to aspolystyrene polymers.

[0025] As set forth above the organic polymer can have differentfunctional groups such as functional groups containing strongly acidicfunctionality such as sulphonic and phosphonic functionality on the sameorganic polymer.

[0026] The weakly acidic cation polymers in general have carboxylicfunctionality and/or the sodium salt associated with the organicpolymer. Typical examples of such polymers are those derived fromunsaturated carboxylic acids such as acrylic, methacrylic or maleiccrosslinked with another monomer such as divinylbenzene or ethylenedimethacrylate. The preferred organic polymers containing cationfunctionality are the strongly acidic cation polymers having sulfonicacid functionality.

[0027] As set forth above, the organic polymer can have functionalityhaving a preferential affinity for soluble metal impurity anions, i.e.the anion associated with the functionality is displaced by the solublemetal impurity anion in the electrolyte. The organic polymers havinganion functionality can have both strongly basic and weakly basic anionfunctionality. Typical examples of strongly basic anion containingfunctionality are those having an ammonium functionality associated withthe organic polymer. As set forth above, the anion associated with thefunctionality, typically sulfate or chloride, is displaced by the metalanion within the electrolyte. Typical ammonium groups associated withthe polymer include trimethyl ammonium ion and dimethylethanol ammoniumion. Other groups include isothiouronium and derivatives thereof.Typical examples of organic polymers are polystyrene cross-linked withdivinylbenzene. The ammonium ion with an appropriate anion can beattached directly to, for example, the aromatic ring of the polystyreneor through, for example, a methylene bridge. Typical examples of weaklybasic polymers having anion functionality are polymers, which containtertiary aliphatic or aromatic aliphatic amine functionalities on thepolymer such as polystyrene or a polyunsaturated carboxylic acids. Suchpolymers are typically cross-linked with a cross-linking agent such asthe cross-linking agents referred to above. Further, the polymer basicanion functionality can be obtained through aliphatic polyaminecondensation reactions to produce the organic polymer. Typically, theweak base anion resins contain primary, secondary and/or tertiary aminegroups generally as a mixture. Typical examples of such amine groups aretrimethyl amine and dimethylethanolamine. The preferred organic polymershaving anion type functionality are the strongly basic anion containingfunctionality particularly for their strong binding and low release ordesorption of metal impurity properties preferably having ammoniumfunctionality, particularly for incorporation into the negative plates.Since the electrolyte in the lead acid battery is sulfuric acid, it ispreferred to use sulfate as the anion to be displaced by metal anion.

[0028] As set forth above the organic polymers can contain primarysecondary or tertiary amine groups including aliphtaic polyaminefunctionality. Further as set forth above, such organic polymers cancontain aliphatic amine functionality. Further, as set forth above suchpolymers can contain amine functionality with acid functionality.Particularly preferred functionalities associated with the organicpolymer which contain both amine and acidic functionality are thosecontaining secondary and tertiary amine functionality and strong acidfunctionality, such as for example, the examples set forth above.

[0029] A particularly preferred class of aliphatic aromatic aminefunctionality are those having amino pyridine groups associated with theorganic polymer. Examples of such groups can be represented by theformula.

[0030] where in R is preferably an aliphatic substituent, an aliphaticpolyamino substituent or a 2-picolene containing substituent R′ ispreferably alkylene, preferably methyleneand R″ is a non-substantiallyinterfering substituent, preferably hydrogen. Particularly preferredadditives are organic polymers having functionality from 2-picolylamine,N-methly-2-picolylamine, N-2hydroxyethyl)-2-picolylamine,N-(2-methylaminoethyl)-2-picolylamine and bis-(2-picolyl)amine.

[0031] The aromatic aliphatic amine functionalities particularly the2-picolylamine, such as bis-(2-picoly)amine, are particularly useful ininhibiting the detrimental effects of copper and nickel.

[0032] As set forth above the organic polymers can contain primarysecondary or tertiary amine groups including aliphtaic polyamenefunctionality. Further as set forth above, such organic polymers cancontain aliphatic amine functionality. Further, as set forth above suchpolymers can contain amine functionality with acid functionality.Particularly preferred functionalities associated with the organicpolymer which contain both amine and acidic functionality are thosecontaining secondary and tertiary amine functionality and strong acidfunctionality, such as for example, the examples set forth above.

[0033] The organic polymers having functional groups with affinity formetal impurity are typically within the particle size ranges,porosities, surface areas, additive concentration and such otherphysical properties set forth below with respect to porosity additives.The porosity of the preferred organic polymers can vary over a widerange such as within the ranges set forth below with respect to microand macro porosity. The porosity of the preferred organic polymers isthat which allows the metal impurity ion, cation and/or anion topermeate the organic polymer particle thereby affording good contactwith the functional groups attached to the external and internalsurfaces of the particles. The total displacement capacity of theorganic polymer having such functional groups is typically greater thanone milliequivalent of displaceable anion or cation per gram of polymer,preferably greater than three and still more preferably greater thanfive.

[0034] As set forth above, the porous organic polymers having functionalgroups can be incorporated into porous type separators such as porousmats or felts that are used in valve regulated recombinant batteries.The functional groups associate with the sulfuric acid electrolyte andchange in particle size and pore size as the acid molarity in thebattery changes during discharge and charge cycling. Thus at low acidmolarities typical of the discharge state of a battery the porousorganic polymers will have a larger particle size and larger pores asthe functional groups associate with the electrolyte. It is believedthat the increase in particle size is due to the hydration of thefunctional groups, which is significantly more pronounced at low acidconcentrations as opposed to the high acid concentration representativeof a fully charged battery. As set forth above, the porosity of theorganic polymers can be microporous including gels, macroporous andcombinations of the porosities. It is preferred that the porous organicpolymers have microporosity and/or a combination of microporosity withmacroporosity, weak acid and/or weak anion functional groups and lowcross-linking such as by the various cross-linking agents set forthabove. It is preferred that the amount of cross-linking in the porouspolymer is less than about 10% preferably less than 6% and still morepreferably less than 4%. Further, as set forth above, the weakly acidicfunctional groups are preferred particularly the carboxylic functionalgroup. The above preferred properties of the porous organic polymers andfunctional groups improve the overall change in particle size and poresize, i.e. increases such changes when comparing the particle sizes atthe conditions of acid molarity during discharge and charge.

[0035] It has been found that the ability of the particle size to belarger at discharge conditions of the battery alters the porosity of theseparator and controls the oxygen transport from the positive plate tothe negative plate for recombination particularly during the chargingregime wherein excessive oxygen transport to the negative plate reducesand/or adversely effects the ability of the negative plate to berecharged fully, i.e. the production of water from oxygen becomespreferential over the conversion of lead sulfate to sponge lead in thenegative plate. Further, the porous organic polymers have functionalgroups which are typically of hydrophilic character and porosity, whichallows for improved distribution of the electrolyte in the separator andoverall improvement in electrolyte utilization in the battery.

[0036] Any suitable positive active electrode material or combination ofsuch materials useful in lead-acid batteries may be employed in thepresent invention. The positive active electrode material can beprepared by conventional processes. For example, a positive activeelectrode material precursor paste of lead sulfate and litharge (PbO) inwater can be used, or conventional pastes, such as those produced fromleady oxide, sulfuric acid and water, can be used. After the paste isapplied to the grid material, it is dried and cured. The precursor pastemay be converted to lead dioxide by applying a charging potential to thepaste.

[0037] Any suitable negative active electrode material useful inlead-acid batteries may be employed in the present invention. Oneparticularly useful formed negative active electrode material compriseslead, e.g., sponge lead. Conventional lead paste prepared from leadyoxide, sulfuric acid, water and suitable expanders can be used.

[0038] Each of the cells of a lead acid battery further includes anon-electrically conductive separator acting to separate the positiveand negative electrodes of the cell and to hold electrolyte. Anysuitable material may be used as a separator provided that it has nosubstantial detrimental effect on the functioning of the cells orbattery. Typical examples of separator material for batteries includeglass fiber, sintered polyvinyl chloride and microporous polyethylene,which have very small pore sizes. Certain of these separators are formedas envelopes, with the pasted plates inside and the separator edgessealed permanently. Typically only the positive plates are encased inthe separator. Separators uses for sealed lead-acid batteries operatingon the oxygen recombination principle, i.e., oxygen recombinantbatteries include one or more layers of silica-based glass, preferablyseparators formed of a highly absorptive porous mat of acidwettablebinder free microfine glass fibers. Typically, a mix of fibers may beemployed whose individual fibers have an average diameter in the rangeof a bout 0.2 to about 10 microns, more preferably about 0.4 to 5.0microns, with possible minor amounts of larger gauge fibers tofacilitate production of the mat. The porosity is preferably high, morepreferably in the range of about 80% to about 98% and still morepreferably about 85% to about 95%, if in the compressed state in thecell (slightly higher in the uncompressed state). The separatorpreferably has a relatively high surface area, more preferably in therange about 0.1 to about 20 m2/g, which facilitates the absorption andretention of relatively large amounts of acid electrolyte volumetricallywhile, if desired, still having a substantial unfilled pore volumepermeable to oxygen for transport directly through the separator forconsumption at the negative electrode. The particularly preferredseparator materials have a surface area as measured by the BET method ofin the range about 0.2 to about 3.0 m2/g., 30 especially about 1.0 toabout 2.0 m2/g.

[0039] As set forth above metal impurities are particularly detrimentalin sealed lead acid batteries operating on the oxygen recombinationprincipal, i.e. recombinant batteries. A number of impurity metals canexert a deleterious effect on the performance of recombinant batteriesby for example, effecting one of more of the performance requirements ofthe recombinant batteries such as by increasing oxygen, evolution at thepositive electrode, increasing hydrogen evolution at the negativeelectrode, inhibiting oxygen recombination at the negative electrode andin increasing the amount of water lost by the battery. Typical examplesof metals that are particularly deleterious in recombinant batteries arearsenic, antimony, cobalt, chromium, nickel and tellurium.

[0040] As set forth above, the metal impurity inhibiting additives canbe incorporated directly into the positive active material or negativeactive material for reducing the detrimental effects of the solublemetal impurity on the negative plates. Further, the metal impurityinhibiting additives, as set forth above, can be coated on the separatorsuch as the glass fiber mats used in lead acid batteries. Further, themetal impurity inhibiting additives can be incorporated into the porouspolymeric separators, such as polyvinyl chloride and microporouspolyethylene. Typical concentrations of the additives associated withthe separator is less than about 10 wt % preferably less than about 5 wt% basis the weight of the separators. The preferred metal impurityinhibiting additives are the porous organic polymers, which allow forthe inhibiting effect of the additives while not detrimentally adverselyeffecting the flow of electrolyte from and/or through the separator tothe positive and negative plates.

[0041] As set forth above, the organic polymers containing functionalgroups for controlling oxygen during the oxygen recombination cycle andproviding for improved electrolyte distribution in the separator areincorporated into the recombinant battery separator. The separators canbe for example porous mats and/or felts having microfine fiberstypically glass fibers, organic fibers and/or mixtures of thecombination of fibers. The fiber mats have an unfilled pore volume,which allows oxygen to be transported directly though the separator forconsumption at the negative electrode. State of the art separators canbe manufactured binder free and/or with binder. Battery separators ofthis type can be manufactured on paper making machines or in combinationwith a conventional melt blowing apparatus to produce polymer filamentswhich are deposited on a moving conveyer to form a flat mat or felt.

[0042] In another aspect for manufacturing tin dioxide coated poroussubstrates, the process comprises contacting a porous substrate with acomposition comprising a tin oxide precursor, such as tin chlorideforming components, including stannic chloride, stannous chloride, tincomplexes and mixtures thereof, preferably stannous chloride, atconditions, preferably substantially non-deleterious oxidizingconditions, more preferably in a substantially inert environment oratmosphere, effective to form a tin oxide precursor-containing coating,such as a stannous chloride-containing coating, on at least a portion ofthe substrate. The substrate is preferably also contacted with at leastone dopant-forming component, such as at least one fluorine component,at conditions, preferably substantially non-deleterious oxidizingconditions, more preferably in a substantially inert atmosphere,effective to form a dopant forming component-containing coating, on atleast a portion of the substrate. The coated porous particles areparticularly useful in a number of applications, particularly lead acidbatteries, for example, monopolar and bipolar batteries, catalyst,resistance heating elements, electrostatic dissipation elements,electromagnetic interference shielding elements, electrostatic bleedelements, protective coatings, field dependent fluids and the like. Inpractice the particles, which are preferred for use in such applicationsin general have an average length in the range of from about 20 micronsto about 7 mm and an average thickness in the range of from about 20microns to about 7 mm, the average length and thickness being differentor the same depending on particle geometry and application.

[0043] As set forth above, the substrate can be optimized for aparticular application and the particular electrical and/or mechanicalrequirements associated with such end use application. For example, inapplications in which the particles are combined with other materials,such as polymers and positive active material of a lead acid battery anddepending on the requirements of the application, ranges of from about 3microns to about 300 microns, or even less than about 5 microns,typically ranges of from about 3 microns to about 150 microns or fromabout 5 microns to about 75 microns are useful. The porous inorganicsubstrates, can be characterized by bulk density (gm/cc) which is theweight or mass per unit volume considered only for the particle itself,i.e., includes the internal pore volume, surface area (M2/gm), totalpore volume (cc(hg)/gm), pore size distribution and percent apparentporosity. In general, it is preferred that the bulk density be fromabout 3% to about 85% more preferably from about 10% to about 70%, morepreferably, from about 10% to about 60% of the true density of thesubstrate material. Bulk densities less -than about 5% are also useful.In addition, the porous substrate can have a wide range of surface area(M2/gm) of from about 0.01 to about 700 preferably having a moderate tohigh surface area, preferably, from about 10 M2/gm to about 600 M2/gm,more preferably, from about 50 M2/gm to about 500 M2/gm.

[0044] The pore volume is preferably from about 0.4 cc/gm to about 3.5cc/gm, or even up to about 5 cc/gm, more preferably from about 0.7 cc/gmto about 4.5 cc/gm more preferably from about 0.7 cc/gm to about 3.25cc/gm. The pore size distribution can vary over a wide range and canhave various distributions including multi-modal, for example,bi-modadistribution of pores including macro pores and micro pores.There ideally exists a relationship between pore diameter, surface areaand pore volume, thus fixing any two variables generally determines thethird. In general, the mean (50%) pore diameter for macro pores, i.e.,generally classified as having a pore diameter greater than about 750angstroms can vary from about 0.075 microns to about 150 microns, morepreferably, from about 0.075 microns to about 10 microns. Microporosity, generally classified as a porosity having a mean pore diameterof less than about 750 angstroms can vary over a wide range. In general,the mean pore diameter for micro porosity can vary from about 20angstroms to about 750 angstroms, more preferably, from about 70angstroms to about 600 angstroms. The ratio of macro to micro porositycan vary over a wide range and depending on the application, can bevaried to provide optimized performance as more fully set forth underthe various applications. In general, the ratio of percent macroporosity to micro porosity expressed as that percent of the totalporosity can vary from about 0% to about 95%, more preferably, fromabout 5% to about 80% macro porosity and from about 100% to about 5%,more preferably from about 95% to about 20% micro porosity.

[0045] As set forth above, the porous substrate can be inorganic forexample, carbon and carbide, i.e., silicon carbide, sulfonated carbonand/or an inorganic oxide. Typical examples of inorganic oxides whichare useful as substrates include for example, substrates containing oneor more alumino silicate, silica, alumina, zirconia, magnesia, boria,phosphate, titania, ceria, thoria and the like, as well as multi-oxidetype supports such as alumina phosphorous oxide, silica alumina, zeolitemodified inorganic oxides, e.g., silica alumina, perovskites, spinels,aluminates, silicates, e.g., zirconium silicate, mixtures thereof andthe like. A particularly unique porous substrate is diatomite, asedimentary rock composed of skeletal remains of single cell aquaticplants called diatoms typically comprising a major amount of silica.Diatoms are unicellular plants of microscopic size. There are manyvarieties that live in both fresh water and salt water. The diatomextracts amorphous silica from the water building for itself whatamounts to a strong shell with highly symmetrical perforations.Typically the cell walls exhibit lacework patterns of chambers andpartitions, plates and apertures of great variety and complexityoffering a wide selection of shapes. Since the total thickness of thecell wall is in the micron range, it results in an internal structurethat is highly porous on a microscopic scale. Further, the actual solidportion of the substrate occupies only from about 10-30% of the apparentvolume leaving a highly porous material for access to liquid. The meanpore size diameter can vary over a wide range and includes macroporosityof from about 0.075 microns to 10 microns with typical micron sizeranges being from about 0.5 microns to about 5 microns. As set forthabove, the diatomite is generally amorphous and can develop crystallinecharacter during calcination treatment of the diatomite. For purposes ofthis invention, diatomite as produced or after subject to treatment suchas calcination are included within the term diatomite.

[0046] The particularly preferred macroporous additives for use in theseparator elements of this invention are diatomites obtained from freshwater and which have fiber-like type geometry. By the term fiber-liketype geometry is meant that the length of the diatomite is greater thanthe diameter of the diatomite and in view appears to be generallycylindrical and/or fiber-like. It has been found that these fiber-likefresh water diatomites provide what is believed to be an electrolytepumping type action, which provides for improved distribution ofsulfuric acid electrolyte in the recombinant type separator.

[0047] As set forth above, porous substrate particles can be in manyforms and shapes, especially shapes which are not flat surfaces, i.e.,non line-of-site materials such as pellets, extrudates, beads, includingspheres, flakes, aggregates, rings, saddles, stars and the like. Thepercent apparent porosity, i.e., the volume of open pores expressed as apercentage of the external volume can vary over a wide range and ingeneral, can vary from about 20% to about 92%, more preferably, fromabout 40% to about 90%. In practice, the bead particles, includingspheres, which are preferred for use in certain applications in generalhave a roundness associated with such particles generally greater thanabout 70% still more preferably, greater than about 85% an still morepreferably, greater than about 95%. The bead products of this inventionoffer particular advantages in many of such applications disclosedherein, including enhanced dispersion and rheology.

[0048] Acid resistant inorganic substrates, especially fibers, flakes,and glass fibers, are particularly useful substrates, when the substrateis to be used as a component of a battery, such as a lead-acidelectrical energy storage battery.

[0049] The porous substrate for use in lead-acid batteries, because ofavailability, cost and performance considerations, generally comprisesacid resistant glass, and/or ceramics more preferably in the form ofparticles, for example, fibers, and/or flakes, and/or beads includingspheres and/or extrudates as noted above.

[0050] The solid substrates including organic polymers for use inlead-acid batteries are acid resistant. That is, the substrate exhibitssome resistance to corrosion, erosion, oxidation and/or other forms ofdeterioration and/or degradation at the conditions present, e.g., at ornear the positive plate, negative plate or positive or negative side ofbipolar plates or separator, in a lead-acid battery. Thus, the substrateshould itself have an inherent degree of acid resistance. If thesubstrate is acid resistant, the physical integrity and electricaleffectiveness of the whole present battery element, is better maintainedwith time relative to a substrate having reduced acid resistance. Ifglass or ceramic is used as the substrate particle, it is preferred thatthe glass has an increased acid resistance relative to E-glass.Preferably, the acid resistant glass or ceramic substrate is at least asresistant as is C- or T-glass to the conditions present in a lead-acidbattery. Preferably the glass contains more than about 60% by weight ofsilica and less than about 35% by weight of alumina, and alkali andalkaline earth metal oxides.

[0051] As set forth above, one of the preferred applications for use ofthe porous substrates is in lead acid batteries. Thus, the substratescan be added directly to the positive active material of a lead acidbattery, i.e., the positive electrode to improve battery performance,particularly positive active material utilization efficiency. Oneparticular, unique aspect of the porous substrates is that the substrateis able to provide an internal reservoir for holding sulfuric acidelectrolyte required for carrying out the electrochemical reactions inthe positive active material. More particularly, the porosity improvesoverall, high rate performance of the positive active material, i.e.improved utilization efficiency at varying rates of discharge time,including high rates and at short discharge times.

[0052] As set forth above, the physical properties of the poroussubstrates can vary widely. It is preferred that the substrate havesufficient macro porosity and percent apparent porosity to allow for theutilization of the electrolyte sulfuric acid contained in the poresduring discharge of the positive active material and, in addition, thatthe bulk density be selected to reduce the overall weight of thepositive active material while enhancing the overall performance of thebattery. In general, the preferable percent apparent porosity can varyfrom about 40% to about 92%, more preferably, from about 70% to about90%. The preferred ratio of percent macro porosity to percent microporosity can vary over a wide range and in general is from about 20% toabout 95% macro porosity, more preferably, from about 45% to about 90%macro porosity with the balance being micro porosity. The mean porediameter, particularly mean macro pore diameter, can vary over a widerange with the utilization of electrolyte during the condition of thedischarge of the battery being an important factor i.e., at high ratedischarges, such as cold cranking, high macro porosity is preferred.Preferred mean macro pore diameter is from about 1 micron to about 150microns, more preferably, from about 5 to about 100 microns or even fromabout 0.075 micron to about 10 micron and still more preferably fromabout 0.1 to about 5 microns.

[0053] As set forth above, a particularly preferred substrate is aporous particle, i.e. porous support, particularly beads, includingspheres, extrudates, pellets, rings, saddles, stars, etc., preferablywithin the bulk density, macro porosity, micro porosity, apparentpercent porosity and surface areas as set forth above. The coatedparticles can provide improved performance in various applications,particularly, in the positive active material of lead acid batteries. Asset forth above, the porous substrate can provide a reservoir forelectrolyte sulfuric acid, which participates in the electrochemicalreaction during discharge of the positive active material. Aparticularly unique embodiment of the present invention is the use ofthe porous substrate itself as an additive in the positive activematerial to provide a reservoir of electrolyte sulfuric acid whileproviding a light weight additive for incorporation into the positiveactive material. Such particles are porous and within the ranges as setforth above particularly the preferred ranges. Such porous substratescan be further coated with additional components such as with othersurface components, which may improve recharge, i.e. oxidation as wellas other conductive components. As set forth above, the porous substratewith or without an additional component provides unexpected improvementin the performance of the positive active material, particularly, in thehigh rate discharge conditions such as cold cranking under lower thanambient temperature conditions.

[0054] Another particularly unique embodiment of the present inventionis the use of the porous substrate itself as an additive in the negativeactive material to provide a reservoir of electrolyte sulfuric acidwhile providing a lightweight additive for incorporation into thenegative active material. Such particles are porous and within theranges as set forth above for the porous substrates particularly thepreferred ranges. Such porous substrates can be further coated withadditional components such as other surface components, which mayimprove recharge, discharge and/or overall life of the battery, such asconductive components which are stable at the conditions of the negativeelectrode such as carbon and conductive metals, which coated poroussubstrates are included within the scope of this invention and the termporous substrate. The porous substrate with or without an additionalcomponent provides unexpected improvement in the performance of thenegative active material particularly under cold cranking conditionsparticularly multiple cold cranking under lower that ambient temperatureconditions. As set forth above, the porous substrate can provideunexpected improvement in cold cranking typically 0 degrees F or lowerduring a series of multiple cold cranking. In addition, the poroussubstrates in the negative active material can provide for improvedactive material surface area maintenance and active material morphologymaintenance particularly at elevated temperatures such as from about60-80 degrees C or higher.

[0055] Typically, the porous substrates with or without additionalcomponents are incorporated into the positive and negative activematerial typically at a concentration of up to about 5-wt %, typicallyup to about 3-wt % basis the active material.

[0056] As set forth above, it is preferred that the porous substrateparticles have sufficient macroporosity and percent apparent porosityfor the utilization of the electrolyte sulfuric acid contained in thepores during discharge of the active material. Further, as set forthabove, the preferred mean macropore diameter is from about 0.075 micronsto about 10 microns and still more preferably from about 0.1 to about 5microns. Particularly preferred solid porous particles that exhibitsufficient macroporosity to allow for improved utilization of sulfuricacid electrolyte are silica containing inorganic oxides preferablydiatomites particularly those as set forth above and organic basedmaterials particularly polyolefins still more preferably polypropylene.

[0057] The particularly preferred macroporous particles for use in therecombinant battery separators of this invention are those within themacroporosity ranges set forth above and those derived from fresh waterdiatomites having a fiber-like porous structure and organic basedmacroporous particles also having an elongated type geometry, i.e. theaverage length of the particle is greater than the average diameter ofthe base particle. It has been found that the macroporosity and thefiber-like and/or elongated geometry allows for rapid equilibration ofthe electrolyte in the separator and for reducing the adverse effectscaused by stratification of the electrolyte in recombinant separators invalve regulated lead acid batteries.

[0058] As set forth above, the porous substrates are acid resistant andinclude a wide variety of materials, including inorganic and organicbased materials. The porous substrates can be in a wide variety ofshapes, including shapes that are reduced in size during the manufactureof the positive active material, such as in the blending and/or mixingof the porous substrate in positive active material manufacture. It ispreferred that the resulting particles if reduced in size maintainporosity parameters within the ranges as set forth above. It is alsopreferred, that the particles have sufficient stiffness and orresistance to detrimental permanent deformation in order to maintainsufficient porosity for the sulfuric acid in the pores to participate ina number of repetitive discharge and charge cycles, such as greater than50 cycles or even 100 cycles.

[0059] Further unique embodiment of the present invention is the use ofa resilient organic porous substrate which resists detrimental permanentdeformation, maintains sufficient porosity for the sulfuric acid in thepores, has resiliency to be deformed under the conditions of dischargeparticularly mechanical forces in the active material of the lead acidbattery and has resiliency to approach or attain its original geometryupon recharge of the battery. In a lead acid battery, the densities ofthe active material change i.e. lead at a density of 11.34 gram/cc, leadperoxide at a density of 9.4 grams/cc, (negative and positive platerespectively) change during discharge of the battery to lead sulfatehaving a density of 6.2 grams/cc i.e. lead sulfate. Upon recharge, thelead sulfate is converted back to lead and lead peroxide in the negativeand positive plates respectively. The resilient organic poroussubstrates have the ability to be deformed during discharge and approachor attain their original geometry during recharge of the battery. Thechanges in density and the ability of the porous substrate to bedeformed allows for increased availability and a greater amount ofsulfuric acid from the pores of the substrate as a function of time toparticipate in a number of repetitive discharge and charge cyclesleading to increased utilization efficiency. Typical examples ofresilient organic porous substrates are elastomeric or rubber-likeporous substrates wherein the pores allow the sulfuric acid toparticipate in discharge and charge cycles. Further examples of suchorganic resilient porous substrates are organic polymers including forexample organic polymers selected from the group consisting ofpolyolefins, polyvinyl polymers, -phenol formaldehyde polymers,polyesters, polyvinylesters, cellulose and mixtures thereof. Thepolymers are selected to be acid resistant and compatible with theactive material at the conditions of the electrode in which they are incontact. Various resilient organic porous substrates particularly porousparticles can be produced using suspension polymerization of a dispersedphase consisting of monomers, cross-linking agents, initiators i.e.catalysts and a co-solvent that functions to aid pore formation. Theparticle size, pore volume, pore size distribution and macroporosity canbe varied within the ranges as set forth above. Such resilient organicporous substrates including particles as set forth above have geometriesand are typically used within the ranges as set forth above for thecoated porous substrates, particularly the preferred ranges and, as setforth above, as to their use in positive active and negative activematerial. Depending on the particular active material in which suchresilient porous substrates are incorporated, such porous substrates canbe further coated with additional components such as with other surfacecomponents, which may improve overall properties such as discharge,recharge and life of the active materials.

[0060] The particularly preferred organic macroporous particles for usein the recombinant battery separators of this invention are those thatare resilient. The resilient macroporous particles resist detrimentalpermanent deformation and maintain sufficient porosity for the sulfuricacid in the pores. Further, the resiliency allows the particles to becompressed under the separator compression pressures that are used inrecombinant batteries and to have improved wet compression resistanceunder compression loads. Thus, the resiliency of the macroporousparticles allows the separator to be compressed and for the macroporousparticles to exert a positive pressure against the positive and negativeplates of the recombinant battery thereby providing an improvement inthe life of the recombinant battery by reducing the tendency of theactive material to shed from the positive and negative plates as theseparator compression is reduced over the life of the battery.

[0061] As set forth above, the porous substrates including resilientporous substrates can be incorporated into the positive and negativeactive material. The various porous substrates provide a reservoir ofelectrolyte sulfuric acid in the active material. The reservoir ofsulfuric acid in the porous substrates can be added to the poroussubstrate prior to the addition of the porous substrate to the positiveand negative active material or incorporated into the porous substratefrom the sulfuric acid electrolyte present in the lead acid battery.Further, other liquids such as water can be substituted for sulfuricacid if a liquid is added to the porous substrate prior to the additionof the porous substrate to the active material. As is recognized bythose of skill in the art, only liquids which do not have an adversedetrimental effect on the performance of the battery should be added tothe porous substrate prior to addition to the active material.

[0062] In a still further embodiment and as is set forth above, theporous substrate particles can be coated with another material. One suchmaterial is a component which gives hydrophobic character to the poroussubstrate, i.e. the porous substrate with the component is not water wetto the same degree as without the component. Such change to hydrophobiccharacter can enhance the flow of electrolyte within the active materialby limiting the bonding of the active material to the pores present inthe porous particles and to particle surfaces. A particularly preferredcomponent is a silica based size having hydrophobic alkyl groups such asmethyl, ethyl or isooctyl which provide for hydrophobic character on thesurface of the porous particles. Many of the organic porous particleswithin the scope of this invention have inherent hydrophobic propertiessuch as the polyolefins whereas others have a combination of hydrophilicand hydrophobic properties. As set forth above, it is preferred that theporous particles have sufficient hydrophobic character to reduce thepermanent bonding of the active material to the surfaces of the porousparticles particularly the pores of the particles. The reduced bondingof the active material to the porous particles allows for improveddiffusion of the sulfuric acid electrolyte to the interior of the activematerial associated with the positive and/or negative plate.

[0063] Further, the macroporous particles for use in recombinantseparators have significantly improved controlled wetting by sulfuricacid electrolyte at the varying acid molarities of the lead acid batterywhen the macroporous particles have at least a part hydrophobiccharacter, for example, a combination of hydrophilic and hydrophobicproperties and wherein the hydrophobic character allows for a reductionin permanent bonding to other solid type material used in lead acidbatteries particularly the various fiber type material that makes up therecombinant separator.

[0064] As set forth above, the particularly preferred macroporousparticles are those derived from fresh water diatomites having afiber-like such as cylindrical-like porous structure and organic porouspolymers having an elongated structure wherein the porosity ismacroporosity and the particles have at least part hydrophobic characterto provide controlled wetting by the sulfuric acid electrolyte and areduction in any bonding of the macroporous particles to the recombinantbattery separator. Further, it is preferred that the macroporousadditives be incorporated into the recombinant battery separator whileminimizing the use of any binder preferably no binder.

[0065] As set forth above, the additives are typically incorporated intothe positive and negative active material at a concentration of up toabout 5-wt %. The porous particle additives and the antimony inhibitingadditives are incorporated during battery manufacture preferably duringthe production of the paste prior to application on the grid material.The additives can be incorporated into, for example, the lead, leadyoxide powders to which the sulfuric acid and water are added.Alternatively, the additives can be mixed into the precursor paste priorto applying on the grid material. It is preferred that the additives beincorporated such as to provide a uniform distribution of the additiveparticles throughout the entire paste, active material.

[0066] Further, the porous substrate as set forth above can be an acidresistant organic material, including organic polymeric materials as setforth above. Preferred polymers are polyolefin polymers, polyvinylpolymers, phenolformaldehyde polymers, polyesters, polyvinylesters andmixtures thereof. Preferred polymers are polyolefins, preferablypolypropylene, phenolformaldehyde polymers and polyvinylester,particularly modacrylic polymers.

EXAMPLE 1

[0067] A separator battery element is manufactured from a glass-mathaving a nominal thickness of 48 mils and a microporous rubber separatorhaving a thickness of 85 mils. The glass-mat and rubber separator have amean pore diameter less than 5 microns. A powdered organic polymerhaving a size distribution of from 50 to 125 microns prepared frompolystyrene and cross-linked with divinylbenzene having amino methylenephosphonic functional groups, is sprayed onto the glass-mat in anaqueous slurry. A noninterfering polymer is incorporated into the slurryand has an electrostatic charge opposite that of the metal inhibitingpolymer. The charge differences allow the formation of a porous floc onthe glass-mat.

[0068] The glass-mat and separator are combined by the application of anadhesive followed by mat compression. The organic polymer having thephosphonic functional groups is on the interior of the glass-mat facingthe inner surface of the separator. The separator is assembled into a12-volt battery with 6% antimony grids for positive plates and negativegrids containing no antimony. Trace amounts of nickel are also presentin the lead. The detrimental effects of nickel and antimony on thenegative plate are inhibited by the additive in the separator.

EXAMPLE 2

[0069] A separator battery element is manufactured from a glass-mathaving a nominal thickness of 48 mil. and a microporous polyethyleneseparator having a thickness of 85mils. The glass-mat and separator havea mean pore diameter less than 5 microns. A powdered organic polymerhaving a size distribution of from 50 to 125 microns prepared frompolystyrene and cross-linked with divinylbenzene having gem phosphonicfunctional groups, is sprayed onto the glass-mat in an aqueous slurry. Anoninterfering polymer is incorporated into the slurry and has anelectrostatic charge opposite that of the metal inhibiting polymer. Thecharge differences allow the formation of a porous floc on theglass-mat. The glass-mat and separator are combined by the applicationof an adhesive followed by mat compression. The organic polymer havingthe phosphonic functional groups is on the interior of the glass-matfacing the inner surface of the separator. The separator is assembledinto a 12-volt battery with 6% antimony grids for positive plates andnegative grids containing no antimony. Trace amounts of nickel is alsopresent in the lead. The detrimental effects of nickel and antimony onthe negative plate are inhibited by the additive in the separator.

EXAMPLE 3

[0070] The separator element of example 1 was modified by using a secondmicroporous glass-mat as a replacement for the rubber separator. Theseparator is assembled into a 12-volt battery using the same negativeand positive grid plates as example 1. The detrimental effects of nickeland antimony on the negative plate are inhibited.

EXAMPLE 4

[0071] A macroporous amino phosphonic divinylbenzene cross-linkedpolystyrene additive was compounded with a number of different polymermaterials used commercially for the manufacture of battery separators.This additive was designed at a particle size distribution to provideincreased surface area for the additive and to be electrolyte accessiblein the separator polymer matrix.

[0072] The porosity of the polymeric matrix was designed so that theadditive was present in the channels and pores of the separator and wasaccessible to the electrolyte as opposed to the additive being totallysurrounded and encapsulated by the polymeric matrix. In the latter casethe additive would not be accessible to the metal contaminate dissolvedin the electrolyte. A number of different polymeric separators wereevaluated including a polyethylene separator, a natural rubbercompounded separator and a polyvinyl chloride separator. The separatorswere evaluated in a continuous filtration column in order to determinethe binding efficiency and capacity of the additive as a function of thetype of additive, it's concentration and the accessibility of theadditive in the polymeric matrix to electrolyte.

[0073] In the evaluation protocol, two blank polyethylene separatorswere mounted first on a four-inch diameter filtration column in order tobe able to better control the solution flow through the column device.

[0074] Solution flow rate was also controlled via a vacuum applied tothe collection vessel. The solution flow rate that allowed separators tobe characterized for overall metal binding efficiency was 0.5 ml/min. Ontop of the polyethylene separators was placed four polyvinylchloride(PVC) separators containing 3.9-wt % additive and weighing a total of15.2 grams. In the apparatus, the PVC separators were caulked withsilicone material at the column interface in order to prevent leakage. Astock antimony (III) soln. was used in all evaluations and had aconcentration of 20.4 mg/L SB (III) ion in 30-wt. % sulfuric acid. A1-cm liquid level was maintained on the separator by continuous additionof solution, to provide a constant pressure. The filtrate through thecolumn was monitored every 60 minutes to determine the concentration ofantimony in the filtrate. Over the first two and one-half hours, theantimony level in the filtrate was below the detection of the ICP unit.At four and one-half hours, there was a residual concentration of 0.7mg/L of antimony. This represents a 97% capture efficiency over the lasthour on a single pass. The data obtained using the additive at the sameconcentration as would be present in the separator showed a captureefficiency on 94% on a single pass. In this control evaluation, theadditive was distributed on the top of the polyethylene separatorfollowed by applying two standard PVC separators (without additive) inorder to hold the additive in place. The conclusions from the test wasthat the distribution of the additive in the PVC separator was moreuniform compared to what can be done in the laboratory with theunincorporated additive.

[0075] The major advances that are shown are that the additive is highlyefficient for irreversible binding of antimony when incorporated intothe PVC separator and that the separator manufacturing procedureprovides a very uniform distribution of the additive in the pores andchannels typically greater than 1 micron. Furthermore, the additive washighly accessible to the electrolyte. It was also found that a reducedparticle size and increased surface area improves overall additiveeffectiveness.

[0076] The test protocol was repeated for a polyethylene separatorhaving relatively small pores and a natural rubber compounded separator.The results on capture efficiency showed a very low capture efficiencyfor the polyethylene separator compounded with 7.5-wt % additive and arelatively low to moderate capture efficiency for the natural rubberseparator which has intrinsic metal control capacity from the rubber. Apost mortem analysis was done on both the PVC and polyethylene separatorand it was determined that the manufacturing process for thepolyethylene separator showed total encapsulation of the additive withvery fine pores less than 0.1 microns and that the additive was notsubstantially electrolyte accessible. The photomicrographs for the PVCseparator showed essentially the entire additive particle accessible tothe electrolyte within the pores and channels of the separator.

EXAMPLE 5

[0077] An evaluation protocol was undertaken to determine theirreversible binding of a metal impurity silver at a typical acidconcentration of 38-wt % sulfuric acid. The sulfuric acid solution had21.4 parts per million (ppm)of silver ion and 1.1 ppm of lead ion. Thetrace amount of lead ion was added to determine preferential binding ofthe silver metal ion over soluble lead ion.

[0078] To 500 ml of the solution containing the above silver metalimpurity and lead ion was added one gram of a divinylbenzenecross-linked polystyrene containing thiouronium functional groups having50% moisture associated with the macroporosity of the additive. Thesolution was stirred for 24 hours at ambient temperature and filtered toremove the macroporous additive. An analysis of the filtrate metalconcentration showed an 86-wt % metal uptake of silver by the additivewith zero uptake of the soluble lead ion. The data shows theirreversible binding of silver to the additive at high hydrogen ion acidconcentration with no detrimental binding of the soluble lead ion resentin the sulfuric acid electrolyte.

[0079] While this invention has been described with respect to variousspecific examples and embodiments, it is to be understood that theinvention is not limited thereto and that it can be variously practicedwithin the scope of the following claims.

What is claimed is:
 1. A battery element useful as a recombinantseparator in a valve regulated lead acid battery having active materialand sulfuric acid electrolyte comprising a recombinant separator and anadditive amount of one or more acid resistant porous organic polymershaving a plurality of functional groups on the internal surfaces of theporous particles, which functional groups associate with the electrolyteto control oxygen diffusion through the separator at the varyingsulfuric acid molarity conditions of the battery provided that said oneor more organic porous polymers are associated with said separator andin contact with the electrolyte to allow said electrolyte tosubstantially permeate the internal surfaces of the porous polymer. 2.The element of claim 1 wherein the organic polymer has weak acidfunctionality.
 3. The element of claim 2 wherein the functionality iscarboxylic.
 4. The element of claim 1 wherein the organic polymer hasanion functionality.
 5. The element of claim 4 wherein the anionfunctionality is weak anion.
 6. The element of claim 1 wherein theorganic polymer is a cross-linked polystyrene and the cross-linking isby divinylbenzene.
 7. The element of claim 3 wherein the organic polymeris a cross-linked polystyrene and the cross-linking is bydivinylbenzene.
 8. The element of claim 5 wherein the organic polymer isa cross-linked polystyrene and the cross-linking is by divinylbenzene.9. The element of claim 1 wherein the organic polymer is a cross-linkedpolymer and the cross-linking is less than about 6%.
 10. The element ofclaim 3 wherein the organic polymer is a cross-linked polymer and thecross-linking is less than about 6%.
 11. The element of claim 7 whereinthe organic polymer is a cross-linked polymer and the cross-linking isless than about 6%.
 12. The element of claim 1 wherein the porousorganic polymers have microporosity.
 13. The element of claim 3 whereinthe porous organic polymers have microporosity.
 14. The element of claim7 wherein the porous organic polymers have microporosity.
 15. A batteryelement useful as a fiber mat recombinant separator in a valve regulatedlead acid battery having active material and sulfuric acid electrolytecomprising a recombinant separator and an additive amount of one or moreacid resistant porous organic polymers having a plurality of functionalgroups on the internal surfaces of the porous particles, whichfunctional groups associate with the electrolyte to control oxygendiffusion through the separator at the varying sulfuric acid molarityconditions of the battery provided that said one or more organic porouspolymers are associated with said separator and in contact with theelectrolyte to allow said electrolyte to substantially permeate theinternal surfaces of the porous polymer.
 16. The element of claim 15wherein the fiber in the fiber mat is selected from the group consistingof glass, organic polymer and mixtures thereof.
 17. The element of claim16 wherein the fibers are predominantly microfine fibers.
 18. Theelement of claim 15 wherein the organic polymer has weak acidfunctionality.
 19. The element of claim 18 wherein the functionality iscarboxylic.
 20. The element of claim 15 wherein the organic polymer hasanion functionality.
 21. The element of claim 20 wherein the anionfunctionality is weak anion.
 22. The element of claim 15 wherein theorganic polymer is a cross-linked polystyrene and the cross-linking isby divinylbenzene.
 23. The element of claim 19 wherein the organicpolymer is a cross-linked polystyrene and the cross-linking is bydivinylbenzene.
 24. The element of claim 21 wherein the organic polymeris a cross-linked polystyrene and the cross-linking is bydivinylbenzene.
 25. The element of claim 15 wherein the organic polymeris a cross-linked polymer and the cross-linking is less than about 6%.26. The element of claim 19 wherein the organic polymer is across-linked polymer and the cross-linking is less than about 6%. 27.The element of claim 21 wherein the organic polymer is a cross-linkedpolymer and the cross-linking is less than about 6%.
 28. The element ofclaim 15 wherein the porous organic polymers have microporosity.
 29. Theelement of claim 19 wherein the porous organic polymers havemicroporosity.
 30. The element of claim 27 wherein the porous organicpolymers have microporosity.
 31. A battery element useful as a fiber matrecombinant separator in a valve regulated lead acid battery havingactive material and sulfuric acid electrolyte comprising a recombinantseparator and an additive amount of one or more acid resistant porousorganic polymers having a plurality of functional groups on the internalsurfaces of the porous particles, which functional groups associate withthe sulfuric acid electrolyte to change the particle size and particlepore size and control oxygen diffusion through the separator at thevarying sulfuric acid molarity conditions of the battery provided thatsaid one or more organic porous polymers are associated with saidseparator and in contact with the electrolyte to allow said electrolyteto substantially permeate the internal surfaces of the porous polymer.32. The element of claim 31 wherein the organic polymer has weak acidfunctionality.
 33. The element of claim 32 wherein the functionality iscarboxylic.
 34. The element of claim 31 wherein the organic polymer hasanion functionality.
 35. The element of claim 34 wherein the anionfunctionality is weak anion.
 36. The element of claim 31 wherein theorganic polymer is a cross-linked polystyrene and the cross-linking isby divinylbenzene.
 37. The element of claim 33 wherein the organicpolymer is a cross-linked polystyrene and the cross-linking is bydivinylbenzene.
 38. The element of claim 35 wherein the organic polymeris a cross-linked polystyrene and the cross-linking is bydivinylbenzene.
 39. The element of claim 31 wherein the organic polymeris a cross-linked polymer and the cross-linking is less than about 6%.40. The element of claim 33 wherein the organic polymer is across-linked polymer and the cross-linking is less than about 6%. 41.The element of claim 35 wherein the organic polymer is a cross-linkedpolymer and the cross-linking is less than about 6%.
 42. The element ofclaim 31 wherein the porous organic polymers have microporosity.
 43. Theelement of claim 33 wherein the porous organic polymers havemicroporosity.
 44. The element of claim 37 wherein the porous organicpolymers have microporosity.